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The high temperature test reactor (HTTR) is a graphite-moderated
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....

 gas-cooled research reactor
Research reactor
Research reactors are nuclear reactors that serve primarily as a neutron source. They are also called non-power reactors, in contrast to power reactors that are used for electricity production, heat generation, or maritime propulsion.-Purpose:...

 in Oarai, Ibaraki
Oarai, Ibaraki
is a town located in Higashiibaraki District, Ibaraki, Japan.As of 2003, the town has an estimated population of 19,606 and a density of 845.45 persons per km²...

, Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 operated by the Japan Atomic Energy Agency
Japan Atomic Energy Agency
The was formed October 1, 2005 by a merger of two previous semi-governmental organizations. While it inherited the activities of both PNC and JAERI, it also inherited the nickname of JAERI, "Genken" 原研, an abbreviated word for "nuclear research"....

. It uses long hexagonal fuel assemblies, unlike the competing pebble bed reactor
Pebble bed reactor
The pebble bed reactor is a graphite-moderated, gas-cooled, nuclear reactor. It is a type of very high temperature reactor , one of the six classes of nuclear reactors in the Generation IV initiative...


HTTR first reached its full design power of 30 MW (thermal) in 1999. Other tests have shown that the core can reach temperatures sufficient for hydrogen production
Hydrogen production
Hydrogen production is the family of industrial methods for generating hydrogen. Currently the dominant technology for direct production is steam reforming from hydrocarbons. Many other methods are known including electrolysis and thermolysis...


Technical details

The primary coolant is helium gas at a pressure of about 4 MPa, the inlet temperature of 395 °C, and the outlet temperature of 850/950 °C. The fuel is uranium oxide (enriched to an average of about 6%).

External links

  • HTTR at the JAEA website.